@
ironclad If I recall correctly, he has been, shall we say, resisting his youthful impulses because there's a lady present.
Then he went to the hot springs, and between this and that, he has had a lot of things to consider(read as: he saw several nekkid or near-nekkid ladies in rapid succession).
So here we are now.
Amazingly, Birdy seems quite oblivious to all of this. Unaware that a teenage male might be affected by BOOBS, and unaware what exactly a boner means.
Is altan anatomy that different from human in spite of appearances, or is she just astonishingly naive?